Audit fixes for election/staking decoupling part 2 (#8167)

* Base features and traits. * pallet and unsigned phase * Undo bad formattings. * some formatting cleanup. * Small self-cleanup. * Make it all build * self-review * Some doc tests. * Some changes from other PR * Fix session test * Update Cargo.lock * Update frame/election-provider-multi-phase/src/lib.rs Co-authored-by: Guillaume Thiolliere <gui.thiolliere@gmail.com> * Some review comments * Rename + make encode/decode * Do an assert as well, just in case. * Fix build * Update frame/election-provider-multi-phase/src/unsigned.rs Co-authored-by: Guillaume Thiolliere <gui.thiolliere@gmail.com> * Las comment * fix staking fuzzer. * cargo run --release --features=runtime-benchmarks --manifest-path=bin/node/cli/Cargo.toml -- benchmark --chain=dev --steps=50 --repeat=20 --pallet=pallet_election_provider_multi_phase --extrinsic=* --execution=wasm --wasm-execution=compiled --heap-pages=4096 --output=./frame/election-provider-multi-phase/src/weights.rs --template=./.maintain/frame-weight-template.hbs * Add one last layer of feasibility check as well. * Last fixes to benchmarks * Some more docs. * cargo run --release --features=runtime-benchmarks --manifest-path=bin/node/cli/Cargo.toml -- benchmark --chain=dev --steps=50 --repeat=20 --pallet=pallet_election_provider_multi_phase --extrinsic=* --execution=wasm --wasm-execution=compiled --heap-pages=4096 --output=./frame/election-provider-multi-phase/src/weights.rs --template=./.maintain/frame-weight-template.hbs * cargo run --release --features=runtime-benchmarks --manifest-path=bin/node/cli/Cargo.toml -- benchmark --chain=dev --steps=50 --repeat=20 --pallet=pallet_election_provider_multi_phase --extrinsic=* --execution=wasm --wasm-execution=compiled --heap-pages=4096 --output=./frame/election-provider-multi-phase/src/weights.rs --template=./.maintain/frame-weight-template.hbs * Some nits * cargo run --release --features=runtime-benchmarks --manifest-path=bin/node/cli/Cargo.toml -- benchmark --chain=dev --steps=50 --repeat=20 --pallet=pallet_staking --extrinsic=* --execution=wasm --wasm-execution=compiled --heap-pages=4096 --output=./frame/staking/src/weights.rs --template=./.maintain/frame-weight-template.hbs * Fix doc * Mkae ci green * Audit fixes for election-provider: part 2 signed phase. * Fix weight * Some grumbles. * Try and weigh to get_npos_voters * Fix build * Fix line width * cargo run --release --features=runtime-benchmarks --manifest-path=bin/node/cli/Cargo.toml -- benchmark --chain=dev --steps=50 --repeat=20 --pallet=pallet_staking --extrinsic=* --execution=wasm --wasm-execution=compiled --heap-pages=4096 --output=./frame/staking/src/weights.rs --template=./.maintain/frame-weight-template.hbs * Fix tests. * Fix build * Reorg some stuff * More reorg. * Reorg done. * Fix build * Another rename * Fix build * Update frame/election-provider-multi-phase/src/mock.rs Co-authored-by: Peter Goodspeed-Niklaus <coriolinus@users.noreply.github.com> * nit * better doc * Line width * Fix build * Self-review * Self-review * Fix wan * cargo run --release --features=runtime-benchmarks --manifest-path=bin/node/cli/Cargo.toml -- benchmark --chain=dev --steps=50 --repeat=20 --pallet=pallet_election_provider_multi_phase --extrinsic=* --execution=wasm --wasm-execution=compiled --heap-pages=4096 --output=./frame/election-provider-multi-phase/src/weights.rs --template=./.maintain/frame-weight-template.hbs * cargo run --release --features=runtime-benchmarks --manifest-path=bin/node/cli/Cargo.toml -- benchmark --chain=dev --steps=50 --repeat=20 --pallet=pallet_staking --extrinsic=* --execution=wasm --wasm-execution=compiled --heap-pages=4096 --output=./frame/staking/src/weights.rs --template=./.maintain/frame-weight-template.hbs * fix build and review comments. * Update frame/election-provider-multi-phase/src/lib.rs Co-authored-by: Shawn Tabrizi <shawntabrizi@gmail.com> * add comment Co-authored-by: Shawn Tabrizi <shawntabrizi@gmail.com> Co-authored-by: Guillaume Thiolliere <gui.thiolliere@gmail.com> Co-authored-by: Parity Benchmarking Bot <admin@parity.io> Co-authored-by: Peter Goodspeed-Niklaus <coriolinus@users.noreply.github.com>
2026-05-30 01:11:04 +00:00 · 2021-03-16 12:44:30 +01:00
parent 49be0579db
commit b6c626399e
32 changed files with 1084 additions and 722 deletions
@@ -26,7 +26,7 @@ sp-std = { version = "3.0.0", default-features = false, path = "../../primitives
 sp-runtime = { version = "3.0.0", default-features = false, path = "../../primitives/runtime" }
 sp-npos-elections = { version = "3.0.0", default-features = false, path = "../../primitives/npos-elections" }
 sp-arithmetic = { version = "3.0.0", default-features = false, path = "../../primitives/arithmetic" }
-sp-election-providers = { version = "3.0.0", default-features = false, path = "../../primitives/election-providers" }
+frame-election-provider-support = { version = "3.0.0", default-features = false, path = "../election-provider-support" }

 # Optional imports for benchmarking
 frame-benchmarking = { version = "3.1.0", default-features = false, path = "../benchmarking", optional = true }
@@ -41,9 +41,9 @@ substrate-test-utils = { version = "3.0.0", path = "../../test-utils" }
 sp-io = { version = "3.0.0", path = "../../primitives/io" }
 sp-core = { version = "3.0.0", path = "../../primitives/core" }
 sp-tracing = { version = "3.0.0", path = "../../primitives/tracing" }
-sp-election-providers = { version = "3.0.0", features = ["runtime-benchmarks"], path = "../../primitives/election-providers" }
+frame-election-provider-support = { version = "3.0.0", features = ["runtime-benchmarks"], path = "../election-provider-support" }
 pallet-balances = { version = "3.0.0", path = "../balances" }
-frame-benchmarking = { path = "../benchmarking" , version = "3.1.0"}
+frame-benchmarking = { version = "3.1.0", path = "../benchmarking" }

 [features]
 default = ["std"]
@@ -60,7 +60,7 @@ std = [
 	"sp-runtime/std",
 	"sp-npos-elections/std",
 	"sp-arithmetic/std",
-	"sp-election-providers/std",
+	"frame-election-provider-support/std",
 	"log/std",
 ]
 runtime-benchmarks = [
@@ -1,6 +1,6 @@
 // This file is part of Substrate.

-// Copyright (C) 2020 Parity Technologies (UK) Ltd.
+// Copyright (C) 2021 Parity Technologies (UK) Ltd.
 // SPDX-License-Identifier: Apache-2.0

 // Licensed under the Apache License, Version 2.0 (the "License");
@@ -19,17 +19,16 @@

 use super::*;
 use crate::Module as MultiPhase;
-
-pub use frame_benchmarking::{account, benchmarks, whitelist_account, whitelisted_caller};
+use frame_benchmarking::impl_benchmark_test_suite;
 use frame_support::{assert_ok, traits::OnInitialize};
 use frame_system::RawOrigin;
 use rand::{prelude::SliceRandom, rngs::SmallRng, SeedableRng};
-use sp_election_providers::Assignment;
+use frame_election_provider_support::Assignment;
 use sp_arithmetic::traits::One;
 use sp_runtime::InnerOf;
 use sp_std::convert::TryInto;

-const SEED: u32 = 0;
+const SEED: u32 = 999;

 /// Creates a **valid** solution with exactly the given size.
 ///
@@ -55,9 +54,9 @@ fn solution_with_size<T: Config>(

 	// first generates random targets.
 	let targets: Vec<T::AccountId> =
-		(0..size.targets).map(|i| account("Targets", i, SEED)).collect();
+		(0..size.targets).map(|i| frame_benchmarking::account("Targets", i, SEED)).collect();

-	let mut rng = SmallRng::seed_from_u64(999u64);
+	let mut rng = SmallRng::seed_from_u64(SEED as u64);

 	// decide who are the winners.
 	let winners = targets
@@ -75,7 +74,7 @@ fn solution_with_size<T: Config>(
 				.choose_multiple(&mut rng, <CompactOf<T>>::LIMIT)
 				.cloned()
 				.collect::<Vec<_>>();
-			let voter = account::<T::AccountId>("Voter", i, SEED);
+			let voter = frame_benchmarking::account::<T::AccountId>("Voter", i, SEED);
 			(voter, stake, winner_votes)
 		})
 		.collect::<Vec<_>>();
@@ -89,7 +88,7 @@ fn solution_with_size<T: Config>(
 				.choose_multiple(&mut rng, <CompactOf<T>>::LIMIT)
 				.cloned()
 				.collect::<Vec<T::AccountId>>();
-			let voter = account::<T::AccountId>("Voter", i, SEED);
+			let voter = frame_benchmarking::account::<T::AccountId>("Voter", i, SEED);
 			(voter, stake, votes)
 		})
 		.collect::<Vec<_>>();
@@ -109,8 +108,9 @@ fn solution_with_size<T: Config>(
 	<DesiredTargets<T>>::put(desired_targets);
 	<Snapshot<T>>::put(RoundSnapshot { voters: all_voters.clone(), targets: targets.clone() });

-	// write the snapshot to staking or whoever is the data provider.
-	T::DataProvider::put_snapshot(all_voters.clone(), targets.clone());
+	// write the snapshot to staking or whoever is the data provider, in case it is needed further
+	// down the road.
+	T::DataProvider::put_snapshot(all_voters.clone(), targets.clone(), Some(stake));

 	let cache = helpers::generate_voter_cache::<T>(&all_voters);
 	let stake_of = helpers::stake_of_fn::<T>(&all_voters, &cache);
@@ -138,10 +138,12 @@ fn solution_with_size<T: Config>(
 		<CompactOf<T>>::from_assignment(assignments, &voter_index, &target_index).unwrap();
 	let score = compact.clone().score(&winners, stake_of, voter_at, target_at).unwrap();
 	let round = <MultiPhase<T>>::round();
+
+	assert!(score[0] > 0, "score is zero, this probably means that the stakes are not set.");
 	RawSolution { compact, score, round }
 }

-benchmarks! {
+frame_benchmarking::benchmarks! {
 	on_initialize_nothing {
 		assert!(<MultiPhase<T>>::current_phase().is_off());
 	}: {
@@ -157,7 +159,7 @@ benchmarks! {
 		assert!(<MultiPhase<T>>::snapshot().is_none());
 		assert!(<MultiPhase<T>>::current_phase().is_off());
 	}: {
-		<MultiPhase<T>>::on_initialize_open_signed();
+		<MultiPhase<T>>::on_initialize_open_signed().unwrap();
 	} verify {
 		assert!(<MultiPhase<T>>::snapshot().is_some());
 		assert!(<MultiPhase<T>>::current_phase().is_signed());
@@ -167,7 +169,7 @@ benchmarks! {
 		assert!(<MultiPhase<T>>::snapshot().is_none());
 		assert!(<MultiPhase<T>>::current_phase().is_off());
 	}: {
-		<MultiPhase<T>>::on_initialize_open_unsigned(true, true, 1u32.into());
+		<MultiPhase<T>>::on_initialize_open_unsigned(true, true, 1u32.into()).unwrap();
 	} verify {
 		assert!(<MultiPhase<T>>::snapshot().is_some());
 		assert!(<MultiPhase<T>>::current_phase().is_unsigned());
@@ -175,21 +177,51 @@ benchmarks! {

 	on_initialize_open_unsigned_without_snapshot {
 		// need to assume signed phase was open before
-		<MultiPhase<T>>::on_initialize_open_signed();
+		<MultiPhase<T>>::on_initialize_open_signed().unwrap();
 		assert!(<MultiPhase<T>>::snapshot().is_some());
 		assert!(<MultiPhase<T>>::current_phase().is_signed());
 	}: {
-		<MultiPhase<T>>::on_initialize_open_unsigned(false, true, 1u32.into());
+		<MultiPhase<T>>::on_initialize_open_unsigned(false, true, 1u32.into()).unwrap();
 	} verify {
 		assert!(<MultiPhase<T>>::snapshot().is_some());
 		assert!(<MultiPhase<T>>::current_phase().is_unsigned());
 	}

+	// a call to `<Pallet as ElectionProvider>::elect` where we only return the queued solution.
+	elect_queued {
+		// assume largest values for the election status. These will merely affect the decoding.
+		let v = T::BenchmarkingConfig::VOTERS[1];
+		let t = T::BenchmarkingConfig::TARGETS[1];
+		let a = T::BenchmarkingConfig::ACTIVE_VOTERS[1];
+		let d = T::BenchmarkingConfig::DESIRED_TARGETS[1];
+
+		let witness = SolutionOrSnapshotSize { voters: v, targets: t };
+		let raw_solution = solution_with_size::<T>(witness, a, d);
+		let ready_solution =
+			<MultiPhase<T>>::feasibility_check(raw_solution, ElectionCompute::Signed).unwrap();
+
+		// these are set by the `solution_with_size` function.
+		assert!(<DesiredTargets<T>>::get().is_some());
+		assert!(<Snapshot<T>>::get().is_some());
+		assert!(<SnapshotMetadata<T>>::get().is_some());
+		<CurrentPhase<T>>::put(Phase::Signed);
+		// assume a queued solution is stored, regardless of where it comes from.
+		<QueuedSolution<T>>::put(ready_solution);
+	}: {
+		let _ = <MultiPhase<T> as ElectionProvider<T::AccountId, T::BlockNumber>>::elect();
+	} verify {
+		assert!(<MultiPhase<T>>::queued_solution().is_none());
+		assert!(<DesiredTargets<T>>::get().is_none());
+		assert!(<Snapshot<T>>::get().is_none());
+		assert!(<SnapshotMetadata<T>>::get().is_none());
+		assert_eq!(<CurrentPhase<T>>::get(), <Phase<T::BlockNumber>>::Off);
+	}
+
 	#[extra]
 	create_snapshot {
 		assert!(<MultiPhase<T>>::snapshot().is_none());
 	}: {
-		<MultiPhase::<T>>::create_snapshot()
+		<MultiPhase::<T>>::create_snapshot().unwrap()
 	} verify {
 		assert!(<MultiPhase<T>>::snapshot().is_some());
 	}
@@ -248,35 +280,8 @@ benchmarks! {
 	}
 }

-#[cfg(test)]
-mod test {
-	use super::*;
-	use crate::mock::*;
-
-	#[test]
-	fn test_benchmarks() {
-		ExtBuilder::default().build_and_execute(|| {
-			assert_ok!(test_benchmark_feasibility_check::<Runtime>());
-		});
-
-		ExtBuilder::default().build_and_execute(|| {
-			assert_ok!(test_benchmark_submit_unsigned::<Runtime>());
-		});
-
-		ExtBuilder::default().build_and_execute(|| {
-			assert_ok!(test_benchmark_on_initialize_open_unsigned_with_snapshot::<Runtime>());
-		});
-
-		ExtBuilder::default().build_and_execute(|| {
-			assert_ok!(test_benchmark_on_initialize_open_unsigned_without_snapshot::<Runtime>());
-		});
-
-		ExtBuilder::default().build_and_execute(|| {
-			assert_ok!(test_benchmark_on_initialize_nothing::<Runtime>());
-		});
-
-		ExtBuilder::default().build_and_execute(|| {
-			assert_ok!(test_benchmark_create_snapshot::<Runtime>());
-		});
-	}
-}
+impl_benchmark_test_suite!(
+	MultiPhase,
+	crate::mock::ExtBuilder::default().build(),
+	crate::mock::Runtime,
+);
@@ -25,7 +25,7 @@ macro_rules! log {
 	($level:tt, $pattern:expr $(, $values:expr)* $(,)?) => {
 		log::$level!(
 			target: $crate::LOG_TARGET,
-			concat!("🗳 ", $pattern) $(, $values)*
+			concat!("[#{:?}] 🗳  ", $pattern), <frame_system::Module<T>>::block_number() $(, $values)*
 		)
 	};
 }
@@ -23,9 +23,10 @@
 //! ## Phases
 //!
 //! The timeline of pallet is as follows. At each block,
-//! [`sp_election_providers::ElectionDataProvider::next_election_prediction`] is used to estimate
-//! the time remaining to the next call to [`sp_election_providers::ElectionProvider::elect`]. Based
-//! on this, a phase is chosen. The timeline is as follows.
+//! [`frame_election_provider_support::ElectionDataProvider::next_election_prediction`] is used to
+//! estimate the time remaining to the next call to
+//! [`frame_election_provider_support::ElectionProvider::elect`]. Based on this, a phase is chosen.
+//! The timeline is as follows.
 //!
 //! ```ignore
 //!                                                                    elect()
@@ -149,7 +150,8 @@
 //!    are helpful for logging and are thus nested as:
 //!    - [`ElectionError::Miner`]: wraps a [`unsigned::MinerError`].
 //!    - [`ElectionError::Feasibility`]: wraps a [`FeasibilityError`].
-//!    - [`ElectionError::OnChainFallback`]: wraps a [`sp_election_providers::onchain::Error`].
+//!    - [`ElectionError::OnChainFallback`]: wraps a
+//!      [`frame_election_provider_support::onchain::Error`].
 //!
 //! Note that there could be an overlap between these sub-errors. For example, A
 //! `SnapshotUnavailable` can happen in both miner and feasibility check phase.
@@ -184,10 +186,10 @@
 //!
 //! **Recursive Fallback**: Currently, the fallback is a separate enum. A different and fancier way
 //! of doing this would be to have the fallback be another
-//! [`sp_election_providers::ElectionProvider`]. In this case, this pallet can even have the
-//! on-chain election provider as fallback, or special _noop_ fallback that simply returns an error,
-//! thus replicating [`FallbackStrategy::Nothing`]. In this case, we won't need the additional
-//! config OnChainAccuracy either.
+//! [`frame_election_provider_support::ElectionProvider`]. In this case, this pallet can even have
+//! the on-chain election provider as fallback, or special _noop_ fallback that simply returns an
+//! error, thus replicating [`FallbackStrategy::Nothing`]. In this case, we won't need the
+//! additional config OnChainAccuracy either.
 //!
 //! **Score based on (byte) size**: We should always prioritize small solutions over bigger ones, if
 //! there is a tie. Even more harsh should be to enforce the bound of the `reduce` algorithm.
@@ -200,6 +202,15 @@
 //! dependency from staking and the compact solution type. It should be generated at runtime, there
 //! it should be encoded how many votes each nominators have. Essentially translate
 //! <https://github.com/paritytech/substrate/pull/7929> to this pallet.
+//!
+//! **More accurate weight for error cases**: Both `ElectionDataProvider` and `ElectionProvider`
+//! assume no weight is consumed in their functions, when operations fail with `Err`. This can
+//! clearly be improved, but not a priority as we generally expect snapshot creation to fail only
+//! due to extreme circumstances.
+//!
+//! **Take into account the encode/decode weight in benchmarks.** Currently, we only take into
+//! account the weight of encode/decode in the `submit_unsigned` given its priority. Nonetheless,
+//! all operations on the solution and the snapshot are worthy of taking this into account.

 #![cfg_attr(not(feature = "std"), no_std)]

@@ -211,7 +222,7 @@ use frame_support::{
 	weights::Weight,
 };
 use frame_system::{ensure_none, offchain::SendTransactionTypes};
-use sp_election_providers::{ElectionDataProvider, ElectionProvider, onchain};
+use frame_election_provider_support::{ElectionDataProvider, ElectionProvider, onchain};
 use sp_npos_elections::{
 	assignment_ratio_to_staked_normalized, is_score_better, CompactSolution, ElectionScore,
 	EvaluateSupport, PerThing128, Supports, VoteWeight,
@@ -222,6 +233,7 @@ use sp_runtime::{
 		TransactionValidityError, ValidTransaction,
 	},
 	DispatchError, PerThing, Perbill, RuntimeDebug, SaturatedConversion,
+	traits::Bounded,
 };
 use sp_std::prelude::*;
 use sp_arithmetic::{
@@ -261,6 +273,7 @@ struct OnChainConfig<T: Config>(sp_std::marker::PhantomData<T>);
 impl<T: Config> onchain::Config for OnChainConfig<T> {
 	type AccountId = T::AccountId;
 	type BlockNumber = T::BlockNumber;
+	type BlockWeights = T::BlockWeights;
 	type Accuracy = T::OnChainAccuracy;
 	type DataProvider = T::DataProvider;
 }
@@ -436,6 +449,8 @@ pub enum ElectionError {
 	Miner(unsigned::MinerError),
 	/// An error in the on-chain fallback.
 	OnChainFallback(onchain::Error),
+	/// An error happened in the data provider.
+	DataProvider(&'static str),
 	/// No fallback is configured. This is a special case.
 	NoFallbackConfigured,
 }
@@ -563,17 +578,28 @@ pub mod pallet {

 			match current_phase {
 				Phase::Off if remaining <= signed_deadline && remaining > unsigned_deadline => {
-					Self::on_initialize_open_signed();
-					log!(info, "Starting signed phase at #{:?} , round {}.", now, Self::round());
-					T::WeightInfo::on_initialize_open_signed()
+					// NOTE: if signed-phase length is zero, second part of the if-condition fails.
+					match Self::on_initialize_open_signed() {
+						Ok(snap_weight) => {
+							log!(info, "Starting signed phase round {}.", Self::round());
+							T::WeightInfo::on_initialize_open_signed().saturating_add(snap_weight)
+						}
+						Err(why) => {
+							// not much we can do about this at this point.
+							log!(warn, "failed to open signed phase due to {:?}", why);
+							T::WeightInfo::on_initialize_nothing()
+							// NOTE: ^^ The trait specifies that this is a noop in terms of weight
+							// in case of error.
+						}
+					}
 				}
 				Phase::Signed | Phase::Off
-					if remaining <= unsigned_deadline && remaining > 0u32.into() =>
+					if remaining <= unsigned_deadline && remaining > Zero::zero() =>
 				{
-					let (need_snapshot, enabled, additional) = if current_phase == Phase::Signed {
+					// determine if followed by signed or not.
+					let (need_snapshot, enabled, signed_weight) = if current_phase == Phase::Signed {
 						// followed by a signed phase: close the signed phase, no need for snapshot.
-						// TWO_PHASE_NOTE: later on once we have signed phase, this should return
-						// something else.
+						// TODO: proper weight https://github.com/paritytech/substrate/pull/7910.
 						(false, true, Weight::zero())
 					} else {
 						// no signed phase: create a new snapshot, definitely `enable` the unsigned
@@ -581,15 +607,25 @@ pub mod pallet {
 						(true, true, Weight::zero())
 					};

-					Self::on_initialize_open_unsigned(need_snapshot, enabled, now);
-					log!(info, "Starting unsigned phase({}) at #{:?}.", enabled, now);
+					match Self::on_initialize_open_unsigned(need_snapshot, enabled, now) {
+						Ok(snap_weight) => {
+							log!(info, "Starting unsigned phase({}).", enabled);
+							let base_weight = if need_snapshot {
+								T::WeightInfo::on_initialize_open_unsigned_with_snapshot()
+							} else {
+								T::WeightInfo::on_initialize_open_unsigned_without_snapshot()
+							};

-					let base_weight = if need_snapshot {
-						T::WeightInfo::on_initialize_open_unsigned_with_snapshot()
-					} else {
-						T::WeightInfo::on_initialize_open_unsigned_without_snapshot()
-					};
-					base_weight.saturating_add(additional)
+							base_weight.saturating_add(snap_weight).saturating_add(signed_weight)
+						}
+						Err(why) => {
+							// not much we can do about this at this point.
+							log!(warn, "failed to open unsigned phase due to {:?}", why);
+							T::WeightInfo::on_initialize_nothing()
+							// NOTE: ^^ The trait specifies that this is a noop in terms of weight
+							// in case of error.
+						}
+					}
 				}
 				_ => T::WeightInfo::on_initialize_nothing(),
 			}
@@ -601,7 +637,7 @@ pub mod pallet {
 				match Self::try_acquire_offchain_lock(n) {
 					Ok(_) => {
 						let outcome = Self::mine_check_and_submit().map_err(ElectionError::from);
-						log!(info, "miner exeuction done: {:?}", outcome);
+						log!(info, "mine_check_and_submit execution done: {:?}", outcome);
 					}
 					Err(why) => log!(warn, "denied offchain worker: {:?}", why),
 				}
@@ -838,32 +874,41 @@ pub mod pallet {
 }

 impl<T: Config> Pallet<T> {
-	/// Logic for `<Pallet as Hooks>::on_initialize` when signed phase is being opened.
+	/// Logic for [`<Pallet as Hooks>::on_initialize`] when signed phase is being opened.
 	///
 	/// This is decoupled for easy weight calculation.
-	pub(crate) fn on_initialize_open_signed() {
+	///
+	/// Returns `Ok(snapshot_weight)` if success, where `snapshot_weight` is the weight that
+	/// needs to recorded for the creation of snapshot.
+	pub(crate) fn on_initialize_open_signed() -> Result<Weight, ElectionError> {
+		let weight = Self::create_snapshot()?;
 		<CurrentPhase<T>>::put(Phase::Signed);
-		Self::create_snapshot();
 		Self::deposit_event(Event::SignedPhaseStarted(Self::round()));
+		Ok(weight.saturating_add(T::DbWeight::get().writes(1)))
 	}

-	/// Logic for `<Pallet as Hooks<T>>::on_initialize` when unsigned phase is being opened.
+	/// Logic for [`<Pallet as Hooks<T>>::on_initialize`] when unsigned phase is being opened.
 	///
-	/// This is decoupled for easy weight calculation. Note that the default weight benchmark of
-	/// this function will assume an empty signed queue for `finalize_signed_phase`.
+	/// This is decoupled for easy weight calculation.
+	///
+	/// Returns `Ok(snapshot_weight)` if success, where `snapshot_weight` is the weight that
+	/// needs to recorded for the creation of snapshot.
 	pub(crate) fn on_initialize_open_unsigned(
 		need_snapshot: bool,
 		enabled: bool,
 		now: T::BlockNumber,
-	) {
-		if need_snapshot {
+	) -> Result<Weight, ElectionError> {
+		let weight = if need_snapshot {
 			// if not being followed by a signed phase, then create the snapshots.
 			debug_assert!(Self::snapshot().is_none());
-			Self::create_snapshot();
-		}
+			Self::create_snapshot()?
+		} else {
+			0
+		};

 		<CurrentPhase<T>>::put(Phase::Unsigned((enabled, now)));
 		Self::deposit_event(Event::UnsignedPhaseStarted(Self::round()));
+		Ok(weight.saturating_add(T::DbWeight::get().writes(1)))
 	}

 	/// Creates the snapshot. Writes new data to:
@@ -871,18 +916,33 @@ impl<T: Config> Pallet<T> {
 	/// 1. [`SnapshotMetadata`]
 	/// 2. [`RoundSnapshot`]
 	/// 3. [`DesiredTargets`]
-	pub(crate) fn create_snapshot() {
-		// if any of them don't exist, create all of them. This is a bit conservative.
-		let targets = T::DataProvider::targets();
-		let voters = T::DataProvider::voters();
-		let desired_targets = T::DataProvider::desired_targets();
+	///
+	/// Returns `Ok(consumed_weight)` if operation is okay.
+	pub(crate) fn create_snapshot() -> Result<Weight, ElectionError> {
+		let target_limit = <CompactTargetIndexOf<T>>::max_value().saturated_into::<usize>();
+		let voter_limit = <CompactVoterIndexOf<T>>::max_value().saturated_into::<usize>();

+		let (targets, w1) =
+			T::DataProvider::targets(Some(target_limit)).map_err(ElectionError::DataProvider)?;
+		let (voters, w2) =
+			T::DataProvider::voters(Some(voter_limit)).map_err(ElectionError::DataProvider)?;
+		let (desired_targets, w3) =
+			T::DataProvider::desired_targets().map_err(ElectionError::DataProvider)?;
+
+		// defensive-only
+		if targets.len() > target_limit || voters.len() > voter_limit {
+			debug_assert!(false, "Snapshot limit has not been respected.");
+			return Err(ElectionError::DataProvider("Snapshot too big for submission."));
+		}
+
+		// only write snapshot if all existed.
 		<SnapshotMetadata<T>>::put(SolutionOrSnapshotSize {
 			voters: voters.len() as u32,
 			targets: targets.len() as u32,
 		});
 		<DesiredTargets<T>>::put(desired_targets);
 		<Snapshot<T>>::put(RoundSnapshot { voters, targets });
+		Ok(w1.saturating_add(w2).saturating_add(w3).saturating_add(T::DbWeight::get().writes(3)))
 	}

 	/// Kill everything created by [`Pallet::create_snapshot`].
@@ -998,7 +1058,7 @@ impl<T: Config> Pallet<T> {
 	}

 	/// On-chain fallback of election.
-	fn onchain_fallback() -> Result<Supports<T::AccountId>, ElectionError> {
+	fn onchain_fallback() -> Result<(Supports<T::AccountId>, Weight), ElectionError> {
 		<onchain::OnChainSequentialPhragmen<OnChainConfig<T>> as ElectionProvider<
 			T::AccountId,
 			T::BlockNumber,
@@ -1006,23 +1066,27 @@ impl<T: Config> Pallet<T> {
 		.map_err(Into::into)
 	}

-	fn do_elect() -> Result<Supports<T::AccountId>, ElectionError> {
+	fn do_elect() -> Result<(Supports<T::AccountId>, Weight), ElectionError> {
 		<QueuedSolution<T>>::take()
 			.map_or_else(
 				|| match T::Fallback::get() {
 					FallbackStrategy::OnChain => Self::onchain_fallback()
-						.map(|r| (r, ElectionCompute::OnChain))
+						.map(|(s, w)| (s, w, ElectionCompute::OnChain))
 						.map_err(Into::into),
 					FallbackStrategy::Nothing => Err(ElectionError::NoFallbackConfigured),
 				},
-				|ReadySolution { supports, compute, .. }| Ok((supports, compute)),
+				|ReadySolution { supports, compute, .. }| Ok((
+					supports,
+					T::WeightInfo::elect_queued(),
+					compute
+				)),
 			)
-			.map(|(supports, compute)| {
+			.map(|(supports, weight, compute)| {
 				Self::deposit_event(Event::ElectionFinalized(Some(compute)));
 				if Self::round() != 1 {
 					log!(info, "Finalized election round with compute {:?}.", compute);
 				}
-				supports
+				(supports, weight)
 			})
 			.map_err(|err| {
 				Self::deposit_event(Event::ElectionFinalized(None));
@@ -1038,10 +1102,11 @@ impl<T: Config> ElectionProvider<T::AccountId, T::BlockNumber> for Pallet<T> {
 	type Error = ElectionError;
 	type DataProvider = T::DataProvider;

-	fn elect() -> Result<Supports<T::AccountId>, Self::Error> {
-		let outcome = Self::do_elect();
+	fn elect() -> Result<(Supports<T::AccountId>, Weight), Self::Error> {
+		let outcome_and_weight = Self::do_elect();
+		// IMPORTANT: regardless of if election was `Ok` or `Err`, we shall do some cleanup.
 		Self::post_elect();
-		outcome
+		outcome_and_weight
 	}
 }

@@ -1132,13 +1197,13 @@ mod feasibility_check {
 				.compact
 				.votes1
 				.iter_mut()
-				.filter(|(_, t)| *t == 3u16)
+				.filter(|(_, t)| *t == TargetIndex::from(3u16))
 				.for_each(|(_, t)| *t += 1);
 			solution.compact.votes2.iter_mut().for_each(|(_, (t0, _), t1)| {
-				if *t0 == 3u16 {
+				if *t0 == TargetIndex::from(3u16) {
 					*t0 += 1
 				};
-				if *t1 == 3u16 {
+				if *t1 == TargetIndex::from(3u16) {
 					*t1 += 1
 				};
 			});
@@ -1166,7 +1231,7 @@ mod feasibility_check {
 					.compact
 					.votes1
 					.iter_mut()
-					.filter(|(v, _)| *v == 7u32)
+					.filter(|(v, _)| *v == VoterIndex::from(7u32))
 					.map(|(v, _)| *v = 8)
 					.count() > 0
 			);
@@ -1229,7 +1294,7 @@ mod feasibility_check {
 #[cfg(test)]
 mod tests {
 	use super::{mock::*, Event, *};
-	use sp_election_providers::ElectionProvider;
+	use frame_election_provider_support::ElectionProvider;
 	use sp_npos_elections::Support;

 	#[test]
@@ -1401,7 +1466,7 @@ mod tests {

 	#[test]
 	fn fallback_strategy_works() {
-		ExtBuilder::default().fallabck(FallbackStrategy::OnChain).build_and_execute(|| {
+		ExtBuilder::default().fallback(FallbackStrategy::OnChain).build_and_execute(|| {
 			roll_to(15);
 			assert_eq!(MultiPhase::current_phase(), Phase::Signed);

@@ -1409,7 +1474,7 @@ mod tests {
 			assert_eq!(MultiPhase::current_phase(), Phase::Unsigned((true, 25)));

 			// zilch solutions thus far.
-			let supports = MultiPhase::elect().unwrap();
+			let (supports, _) = MultiPhase::elect().unwrap();

 			assert_eq!(
 				supports,
@@ -1420,7 +1485,7 @@ mod tests {
 			)
 		});

-		ExtBuilder::default().fallabck(FallbackStrategy::Nothing).build_and_execute(|| {
+		ExtBuilder::default().fallback(FallbackStrategy::Nothing).build_and_execute(|| {
 			roll_to(15);
 			assert_eq!(MultiPhase::current_phase(), Phase::Signed);

@@ -1432,6 +1497,26 @@ mod tests {
 		})
 	}

+	#[test]
+	fn snapshot_creation_fails_if_too_big() {
+		ExtBuilder::default().build_and_execute(|| {
+			Targets::set((0..(TargetIndex::max_value() as AccountId) + 1).collect::<Vec<_>>());
+
+			// signed phase failed to open.
+			roll_to(15);
+			assert_eq!(MultiPhase::current_phase(), Phase::Off);
+
+			// unsigned phase failed to open.
+			roll_to(25);
+			assert_eq!(MultiPhase::current_phase(), Phase::Off);
+
+			// on-chain backup works though.
+			roll_to(29);
+			let (supports, _) = MultiPhase::elect().unwrap();
+			assert!(supports.len() > 0);
+		})
+	}
+
 	#[test]
 	fn number_of_voters_allowed_2sec_block() {
 		// Just a rough estimate with the substrate weights.
@@ -31,7 +31,7 @@ use sp_core::{
 	},
 	H256,
 };
-use sp_election_providers::ElectionDataProvider;
+use frame_election_provider_support::{ElectionDataProvider, data_provider};
 use sp_npos_elections::{
 	assignment_ratio_to_staked_normalized, seq_phragmen, to_supports, to_without_backing,
 	CompactSolution, ElectionResult, EvaluateSupport,
@@ -60,10 +60,12 @@ frame_support::construct_runtime!(

 pub(crate) type Balance = u64;
 pub(crate) type AccountId = u64;
+pub(crate) type VoterIndex = u32;
+pub(crate) type TargetIndex = u16;

 sp_npos_elections::generate_solution_type!(
 	#[compact]
-	pub struct TestCompact::<u32, u16, PerU16>(16)
+	pub struct TestCompact::<VoterIndex, TargetIndex, PerU16>(16)
 );

 /// All events of this pallet.
@@ -239,6 +241,13 @@ impl multi_phase::weights::WeightInfo for DualMockWeightInfo {
 			<() as multi_phase::weights::WeightInfo>::on_initialize_open_unsigned_without_snapshot()
 		}
 	}
+	fn elect_queued() -> Weight {
+		if MockWeightInfo::get() {
+			Zero::zero()
+		} else {
+			<() as multi_phase::weights::WeightInfo>::elect_queued()
+		}
+	}
 	fn submit_unsigned(v: u32, t: u32, a: u32, d: u32) -> Weight {
 		if MockWeightInfo::get() {
 			// 10 base
@@ -291,18 +300,43 @@ pub struct ExtBuilder {}

 pub struct StakingMock;
 impl ElectionDataProvider<AccountId, u64> for StakingMock {
-	fn targets() -> Vec<AccountId> {
-		Targets::get()
+	fn targets(maybe_max_len: Option<usize>) -> data_provider::Result<(Vec<AccountId>, Weight)> {
+		let targets = Targets::get();
+
+		if maybe_max_len.map_or(false, |max_len| targets.len() > max_len) {
+			return Err("Targets too big");
+		}
+
+		Ok((targets, 0))
 	}
-	fn voters() -> Vec<(AccountId, VoteWeight, Vec<AccountId>)> {
-		Voters::get()
+
+	fn voters(
+		maybe_max_len: Option<usize>,
+	) -> data_provider::Result<(Vec<(AccountId, VoteWeight, Vec<AccountId>)>, Weight)> {
+		let voters = Voters::get();
+		if maybe_max_len.map_or(false, |max_len| voters.len() > max_len) {
+			return Err("Voters too big");
+		}
+
+		Ok((voters, 0))
 	}
-	fn desired_targets() -> u32 {
-		DesiredTargets::get()
+	fn desired_targets() -> data_provider::Result<(u32, Weight)> {
+		Ok((DesiredTargets::get(), 0))
 	}
+
 	fn next_election_prediction(now: u64) -> u64 {
 		now + EpochLength::get() - now % EpochLength::get()
 	}
+
+	#[cfg(any(feature = "runtime-benchmarks", test))]
+	fn put_snapshot(
+		voters: Vec<(AccountId, VoteWeight, Vec<AccountId>)>,
+		targets: Vec<AccountId>,
+		_target_stake: Option<VoteWeight>,
+	) {
+		Targets::set(targets);
+		Voters::set(voters);
+	}
 }

 impl ExtBuilder {
@@ -319,7 +353,7 @@ impl ExtBuilder {
 		<UnsignedPhase>::set(unsigned);
 		self
 	}
-	pub fn fallabck(self, fallback: FallbackStrategy) -> Self {
+	pub fn fallback(self, fallback: FallbackStrategy) -> Self {
 		<Fallback>::set(fallback);
 		self
 	}
@@ -66,8 +66,17 @@ impl<T: Config> Pallet<T> {
 		let iters = Self::get_balancing_iters();
 		// get the solution, with a load of checks to ensure if submitted, IT IS ABSOLUTELY VALID.
 		let (raw_solution, witness) = Self::mine_and_check(iters)?;
+		let score = raw_solution.score.clone();
+
+		let call: <T as frame_system::offchain::SendTransactionTypes<Call<T>>>::OverarchingCall =
+			Call::submit_unsigned(raw_solution, witness).into();
+		log!(
+			info,
+			"mined a solution with score {:?} and size {}",
+			score,
+			call.using_encoded(|b| b.len())
+		);

-		let call = Call::submit_unsigned(raw_solution, witness).into();
 		SubmitTransaction::<T, Call<T>>::submit_unsigned_transaction(call)
 			.map_err(|_| MinerError::PoolSubmissionFailed)
 	}
@@ -413,6 +422,9 @@ mod max_weight {
 		fn on_initialize_open_unsigned_with_snapshot() -> Weight {
 			unreachable!()
 		}
+		fn elect_queued() -> Weight {
+			0
+		}
 		fn on_initialize_open_unsigned_without_snapshot() -> Weight {
 			unreachable!()
 		}
@@ -487,7 +499,7 @@ mod tests {
 	};
 	use frame_support::{dispatch::Dispatchable, traits::OffchainWorker};
 	use mock::Call as OuterCall;
-	use sp_election_providers::Assignment;
+	use frame_election_provider_support::Assignment;
 	use sp_runtime::{traits::ValidateUnsigned, PerU16};

 	#[test]
@@ -18,7 +18,7 @@
 //! Autogenerated weights for pallet_election_provider_multi_phase
 //!
 //! THIS FILE WAS AUTO-GENERATED USING THE SUBSTRATE BENCHMARK CLI VERSION 3.0.0
-//! DATE: 2021-02-12, STEPS: `[50, ]`, REPEAT: 20, LOW RANGE: [], HIGH RANGE: []
+//! DATE: 2021-03-14, STEPS: `[50, ]`, REPEAT: 20, LOW RANGE: `[]`, HIGH RANGE: `[]`
 //! EXECUTION: Some(Wasm), WASM-EXECUTION: Compiled, CHAIN: Some("dev"), DB CACHE: 128

 // Executed Command:
@@ -48,6 +48,7 @@ pub trait WeightInfo {
 	fn on_initialize_open_signed() -> Weight;
 	fn on_initialize_open_unsigned_with_snapshot() -> Weight;
 	fn on_initialize_open_unsigned_without_snapshot() -> Weight;
+	fn elect_queued() -> Weight;
 	fn submit_unsigned(v: u32, t: u32, a: u32, d: u32, ) -> Weight;
 	fn feasibility_check(v: u32, t: u32, a: u32, d: u32, ) -> Weight;
 }
@@ -56,47 +57,52 @@ pub trait WeightInfo {
 pub struct SubstrateWeight<T>(PhantomData<T>);
 impl<T: frame_system::Config> WeightInfo for SubstrateWeight<T> {
 	fn on_initialize_nothing() -> Weight {
-		(23_401_000 as Weight)
+		(22_833_000 as Weight)
 			.saturating_add(T::DbWeight::get().reads(7 as Weight))
 	}
 	fn on_initialize_open_signed() -> Weight {
-		(79_260_000 as Weight)
-			.saturating_add(T::DbWeight::get().reads(7 as Weight))
+		(106_993_000 as Weight)
+			.saturating_add(T::DbWeight::get().reads(8 as Weight))
 			.saturating_add(T::DbWeight::get().writes(4 as Weight))
 	}
 	fn on_initialize_open_unsigned_with_snapshot() -> Weight {
-		(77_745_000 as Weight)
-			.saturating_add(T::DbWeight::get().reads(7 as Weight))
+		(106_490_000 as Weight)
+			.saturating_add(T::DbWeight::get().reads(8 as Weight))
 			.saturating_add(T::DbWeight::get().writes(4 as Weight))
 	}
 	fn on_initialize_open_unsigned_without_snapshot() -> Weight {
-		(21_764_000 as Weight)
+		(21_275_000 as Weight)
 			.saturating_add(T::DbWeight::get().reads(1 as Weight))
 			.saturating_add(T::DbWeight::get().writes(1 as Weight))
 	}
+	fn elect_queued() -> Weight {
+		(7_274_346_000 as Weight)
+			.saturating_add(T::DbWeight::get().reads(2 as Weight))
+			.saturating_add(T::DbWeight::get().writes(6 as Weight))
+	}
 	fn submit_unsigned(v: u32, t: u32, a: u32, d: u32, ) -> Weight {
 		(0 as Weight)
-			// Standard Error: 23_000
-			.saturating_add((4_171_000 as Weight).saturating_mul(v as Weight))
-			// Standard Error: 78_000
-			.saturating_add((229_000 as Weight).saturating_mul(t as Weight))
-			// Standard Error: 23_000
-			.saturating_add((13_661_000 as Weight).saturating_mul(a as Weight))
-			// Standard Error: 117_000
-			.saturating_add((4_499_000 as Weight).saturating_mul(d as Weight))
+			// Standard Error: 19_000
+			.saturating_add((4_017_000 as Weight).saturating_mul(v as Weight))
+			// Standard Error: 66_000
+			.saturating_add((130_000 as Weight).saturating_mul(t as Weight))
+			// Standard Error: 19_000
+			.saturating_add((13_057_000 as Weight).saturating_mul(a as Weight))
+			// Standard Error: 99_000
+			.saturating_add((4_558_000 as Weight).saturating_mul(d as Weight))
 			.saturating_add(T::DbWeight::get().reads(6 as Weight))
 			.saturating_add(T::DbWeight::get().writes(1 as Weight))
 	}
 	fn feasibility_check(v: u32, t: u32, a: u32, d: u32, ) -> Weight {
 		(0 as Weight)
 			// Standard Error: 12_000
-			.saturating_add((4_232_000 as Weight).saturating_mul(v as Weight))
-			// Standard Error: 42_000
-			.saturating_add((636_000 as Weight).saturating_mul(t as Weight))
+			.saturating_add((4_186_000 as Weight).saturating_mul(v as Weight))
+			// Standard Error: 40_000
+			.saturating_add((803_000 as Weight).saturating_mul(t as Weight))
 			// Standard Error: 12_000
-			.saturating_add((10_294_000 as Weight).saturating_mul(a as Weight))
-			// Standard Error: 64_000
-			.saturating_add((4_428_000 as Weight).saturating_mul(d as Weight))
+			.saturating_add((9_806_000 as Weight).saturating_mul(a as Weight))
+			// Standard Error: 61_000
+			.saturating_add((4_156_000 as Weight).saturating_mul(d as Weight))
 			.saturating_add(T::DbWeight::get().reads(3 as Weight))
 	}
 }
@@ -104,47 +110,52 @@ impl<T: frame_system::Config> WeightInfo for SubstrateWeight<T> {
 // For backwards compatibility and tests
 impl WeightInfo for () {
 	fn on_initialize_nothing() -> Weight {
-		(23_401_000 as Weight)
+		(22_833_000 as Weight)
 			.saturating_add(RocksDbWeight::get().reads(7 as Weight))
 	}
 	fn on_initialize_open_signed() -> Weight {
-		(79_260_000 as Weight)
-			.saturating_add(RocksDbWeight::get().reads(7 as Weight))
+		(106_993_000 as Weight)
+			.saturating_add(RocksDbWeight::get().reads(8 as Weight))
 			.saturating_add(RocksDbWeight::get().writes(4 as Weight))
 	}
 	fn on_initialize_open_unsigned_with_snapshot() -> Weight {
-		(77_745_000 as Weight)
-			.saturating_add(RocksDbWeight::get().reads(7 as Weight))
+		(106_490_000 as Weight)
+			.saturating_add(RocksDbWeight::get().reads(8 as Weight))
 			.saturating_add(RocksDbWeight::get().writes(4 as Weight))
 	}
 	fn on_initialize_open_unsigned_without_snapshot() -> Weight {
-		(21_764_000 as Weight)
+		(21_275_000 as Weight)
 			.saturating_add(RocksDbWeight::get().reads(1 as Weight))
 			.saturating_add(RocksDbWeight::get().writes(1 as Weight))
 	}
+	fn elect_queued() -> Weight {
+		(7_274_346_000 as Weight)
+			.saturating_add(RocksDbWeight::get().reads(2 as Weight))
+			.saturating_add(RocksDbWeight::get().writes(6 as Weight))
+	}
 	fn submit_unsigned(v: u32, t: u32, a: u32, d: u32, ) -> Weight {
 		(0 as Weight)
-			// Standard Error: 23_000
-			.saturating_add((4_171_000 as Weight).saturating_mul(v as Weight))
-			// Standard Error: 78_000
-			.saturating_add((229_000 as Weight).saturating_mul(t as Weight))
-			// Standard Error: 23_000
-			.saturating_add((13_661_000 as Weight).saturating_mul(a as Weight))
-			// Standard Error: 117_000
-			.saturating_add((4_499_000 as Weight).saturating_mul(d as Weight))
+			// Standard Error: 19_000
+			.saturating_add((4_017_000 as Weight).saturating_mul(v as Weight))
+			// Standard Error: 66_000
+			.saturating_add((130_000 as Weight).saturating_mul(t as Weight))
+			// Standard Error: 19_000
+			.saturating_add((13_057_000 as Weight).saturating_mul(a as Weight))
+			// Standard Error: 99_000
+			.saturating_add((4_558_000 as Weight).saturating_mul(d as Weight))
 			.saturating_add(RocksDbWeight::get().reads(6 as Weight))
 			.saturating_add(RocksDbWeight::get().writes(1 as Weight))
 	}
 	fn feasibility_check(v: u32, t: u32, a: u32, d: u32, ) -> Weight {
 		(0 as Weight)
 			// Standard Error: 12_000
-			.saturating_add((4_232_000 as Weight).saturating_mul(v as Weight))
-			// Standard Error: 42_000
-			.saturating_add((636_000 as Weight).saturating_mul(t as Weight))
+			.saturating_add((4_186_000 as Weight).saturating_mul(v as Weight))
+			// Standard Error: 40_000
+			.saturating_add((803_000 as Weight).saturating_mul(t as Weight))
 			// Standard Error: 12_000
-			.saturating_add((10_294_000 as Weight).saturating_mul(a as Weight))
-			// Standard Error: 64_000
-			.saturating_add((4_428_000 as Weight).saturating_mul(d as Weight))
+			.saturating_add((9_806_000 as Weight).saturating_mul(a as Weight))
+			// Standard Error: 61_000
+			.saturating_add((4_156_000 as Weight).saturating_mul(d as Weight))
 			.saturating_add(RocksDbWeight::get().reads(3 as Weight))
 	}
 }